Method and device for attenuating pressure surges of liquids flowing inside a liquid conduit

ABSTRACT

A system and a method are provided for attenuating pressure surges of liquids, e.g., of a biologically vulnerable liquid, flowing inside a liquid conduit and for cleaning, in particular sterilizing, the liquid conduit. In particular, the liquid is permitted to swerve, in the event that pressure surges occur, into a gas-filled space communicating with the liquid conduit.

BACKGROUND OF THE INVENTION

The invention relates to a device for attenuating pressure surges ofliquids, e.g. of a biologically vulnerable liquid, flowing inside aliquid conduit and for cleaning, in particular sterilizing, the liquidconduit comprising a bypass conduit that bridges over a section of theliquid conduit, wherein an isolating valve as well as a gas supplyconduit are provided in the liquid conduit between the outlets of thebypass conduit.

For the transport of liquids through liquid conduits, in particular forthe purpose of filling them into containers, the liquids must be broughtto particular flow values by means of control and/or check valves intheir flow, or the flow of the liquids must be interrupted,respectively, for instance, upon reaching a predetermined filling levelin the container. Therefore, pressure variations that are more or lesslarge constantly arise in the liquid conduits. Those variations can bevery substantial and in large filling plants, for instance for thebottling of beer, milk, etc., they may exhibit a pulsatingcharacteristic.

Pressure surges can amount to maximum pressures of more than two and ahalf times the normal liquid-conduit pressure. Thereby, excessive strainis put on the fittings and other appliances such as membrane filters,plate heat exchangers and especially also gaskets. In the case of higherstatic conduit pressures, such pressure surges must be rated as evenmore critical in terms of the hypothesis of fatigue strength.

For the purpose of providing a remedy, it is known to use air vesselsfor attenuating the pressure surges. Such air vessels are indeed aproven and simple attenuation means; however, different pressures in theliquid conduits require differently sized gas spaces in the air vesselwhich exhibit different characteristic frequencies, which may lead toproblems for downstream electronic controls. A further greatdisadvantage of such air vessels is that cleaning is not possible duringan operation cycle. Cleaning an air vessel requires that the same isshut off from the pipeline, whereby, after the cleaning process, thedanger that remains of the detergent are present cannot be ruled out.Complete flushing of the air vessel is feasible only in a time-consumingway.

It has also been attempted to attenuate pressure surges with electronicmethods, i.e. to provide electronic control and attenuation means.Those, however, depend on the velocity of the sensors and actuators ofthe system. Nevertheless, especially in high-frequency oscillations,resonances can occur which often aggravate the problem of pressuresurges. On the other hand, excess attenuation of the system might alsolead to pressure variations which are no longer compensable. In thisconnection, the occurrence of strongly varying frequencies of thepressure surges constitutes a particular problem.

From utility model document AT 001740 U1, a shunt pipeline, i.e. abypass conduit, leading to a liquid conduit such as a beer conduit isknown, which pipeline is filled with gas in the normal state and servesfor the absorption of pressure surges. In that known device, pressuresurges might, however, strike through the bypass conduit. Furthermore,it is cumbersome to carry out a purification, in particular involving asterilization liquid, since, on the one hand, the bypass conduit and, onthe other hand, the liquid conduit are to be treated separately, andfurthermore a product change will result in difficulties as a result ofan inadmissable mixture of the various products successively flowingthrough the liquid conduit.

SUMMARY OF THE INVENTION

The invention aims at avoiding those disadvantages and difficulties andhas as an object to provide a device of the initially described kindwhich not only enables an excellent attenuation of pressure surges butalso a reliable cleaning of the device with simple means so that theapplication is also provided for biologically vulnerable products suchas food products without requiring great efforts. In addition, a productchange should also be feasible without substantially mixing the variousproducts.

According to the invention, the object is achieved in that, after thebypass conduit, a throttle is incorporated in the liquid conduit in theflow direction of the liquid.

By means of the throttle it becomes possible to absorb pressure surgesand hence to direct the major part of an overpressure into the bypass.That produces a particularly good protection for the means to which theliquid conduit leads such as for filtering installations, fillingplants, etc.

A preferred variant of the device according to the invention ischaracterized in that the bypass conduit is optionally divisible intotwo gas-filled spaces, preferably two gas-filled spaces of roughly equalvolumes, by means of an isolating valve, which both communicate with theliquid conduit for the purpose of attenuating pressure surges.

Thereby, it becomes possible to definitely avoid that liquid flows overthe bypass, i.e. to maintain the gas cushion in the bypass in any kindof disturbance. In addition, an optionally provided control valve isprevented from damage. A gas cushion escaping from the bypass andentering the liquid conduit would, for instance, decrease the filteringactivity of a filter provided for filtering the liquid, and anindefinable amount of gas would get lost.

Preferably, a pet cock is in each case provided adjacent to theisolating valve and within the section in the bypass conduit that isformed by the isolating valves.

It thereby becomes possible to carry out a product change preciselywithout cleaning. A product which is different from the previouslyflowing product reaches the filling station, and is stopped there,whereupon the isolating valves of the bypass conduit are closed and thepet cocks of the bypass conduit are opened until the first product hasbeen discharged completely.

Preferred variants of the device according to the invention arecharacterized by a combination of the features described herein.

A suitable embodiment is characterized by one lockable gas supplyconduit running into the bypass conduit in the flow direction before andanother one after the isolating valve dividing the bypass conduit.

Advantageously, the isolating valve provided in the liquid conduit has,in the closed state, a leakage opening enabling a small flow, andsuitably the isolating valve provided in the liquid conduit and in thebypass conduit is alternatively operable by means of a control unit.

As the cleaning medium, a sterilization liquid is preferably provided.The device according to the invention is usable to a particularly highdegree for biologically vulnerable products, in particular foodproducts.

For securing a liquid level, i.e. in order to prevent the same fromrising beyond a predetermined scale, probes for determining a liquidlevel are preferably provided in the bypass conduit at a predetermineddistance from the first and the second isolating valves, with a controlunit suitably being provided which is coupled to at least one of the gassupply conduits leading to the bypass conduit so that, if a liquid levelis indicated, an automatic gas flushing and hence a discharge of liquidfrom the bypass conduit will take place.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in greater detail below by way of thedrawing in which an exemplary embodiment is shown.

FIG. 1 shows a filling plant for fresh milk in schematic representation.

FIG. 2 illustrates the device according to the invention in detail.

FIGS. 3 to 5 show various operating conditions of the device accordingto the invention.

FIG. 6 illustrates a variant of the device.

FIGS. 7 to 10 show pressure surges occurring in the liquid conduit asillustrated in chart form, with FIGS. 7 and 9 illustrating pressuresexperienced with a device made according to the invention and FIGS. 8and 10 illustrating pressures experienced without a device according tothe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the filling plant for a liquid, herein for fresh milk, asillustrated in FIG. 1, fresh milk passes from a storage tank 1 via afeed pump 2 and a liquid conduit 3 to two filling machines 4 in whichmilk bottles or other containers such as laminated cardboards, etc. arefilled intermittently. A device 6 according to the invention is providedbetween the fresh milk tank and the filling plant arranged first in theflow direction 5, which device is indicated only schematically in FIG. 1but is illustrated in detail in FIG. 2. Suitably, the device 6 isincorporated in the liquid conduit right in front of the fillingmachines 4.

According to the embodiment as illustrated in FIG. 2, the device 6according to the invention exhibits a bypass conduit 7 which bridgesover a predetermined section 8 of the liquid conduit 3. In the areawhere the mouths 9 and 10 of the bypass conduit 7 open into the liquidconduit 3, the bypass conduit 7 is provided with a first and a secondisolating valve 11, 12 so that it is possible to separate the bypassconduit 7, with respect to the pipelines, completely from the liquidconduit.

A lockable pet cock 13, 14 is in each case provided in the bypassconduit adjacent to the first and the second isolating valves 11, 12,namely within the section of the bypass conduit 7 formed by the firstand the second isolating valves 11, 12. A third isolating valve 15 islocated in the bypass conduit 7 at about the same distance from theopenings of the bypass conduit 7 (at 9 and 10, respectively) into theliquid conduit 3.

Lockable gas supply conduits 16, 17 running into the bypass conduit 7are provided in the flow direction 5 of the liquid before and after thethird isolating valve 15.

In order to avoid an excessively high liquid level in the bypass conduit7, probes 20 are provided in the same at a predetermined distance 19from the first and the second isolating valves, by means of which probesthe presence of liquid can be determined at the level of the probes 20.If those probes 20 are flushed over by a liquid, those probes 20 giveoff a signal which controls, by means of a control unit 21, the influxof a gas via the gas supply conduits 16 or 17 into the respectiveflooded section of the bypass conduit 7.

In the liquid conduit 3, a fourth isolating valve 22 is incorporated inthe section 8 which is bridged over by the bypass conduit 7, whichfourth isolating valve blocks the main flow, i.e. the liquid flow thatis routed via the liquid conduit 3 to the filling machines 4 or thelike. The valve 22 is configured either as an isolating valve (FIG. 2)or as a control valve such as illustrated in FIG. 6. In one embodimentas an isolating valve, realized as a plug valve, for instance, the slidevalve is preferably provided with a hole, wherein the hole has adiameter ranging, e.g., from a few millimeters to 20 mm. In this way, aslight onward flow of the medium flowing in the liquid conduit isensured, even if the valve is closed. The hole thus forms a leakageopening leaving open a passage for the flow. Furthermore, a throttle 23is incorporated in the liquid conduit in the flow direction after thebypass conduit 7.

The functioning of the device 6 according to the invention is asfollows:

During the normal conveyance of liquid 24 (FIG. 3) via the liquidconduit 3, the first and the second isolating valves 11, 12 are open andthe pet cocks 13, 14 are closed. In the bypass conduit 7 in which thethird isolating valve 15 is closed, gas cushions are present in the twospaces 25, 26 which are formed by the closed third valve, namely in sucha manner that the liquid level 27 is below the probes 20 provided inthose spaces 25, 26. During the conveyance of the liquid 24, the fourthisolating valve 22 is open. Should pressure surges or high-frequencypressure variations occur, those will be absorbed or reduced,respectively, by the gas cushions present in the two gas-filled spaces25, 26 of the bypass conduit 7.

CO₂ or sterile air is preferably used for the production of a gascushion.

The gas pressure of the gas cushions is adapted to the prevailing staticoperating pressure of the liquid in such a way that the liquid level 27will always remain below the probes 20. This condition is illustrated inFIG. 3.

For the purpose of cleaning (FIG. 4) the liquid conduit 3, the first andthe second isolating valves 11, 12 remain open; however, the thirdisolating valve 15 is opened and the fourth isolating valve 22 isclosed. The two pet cocks 13, 14 are temporarily opened or supplied withclock pulses, respectively, in order to likewise remove the previouslyconveyed liquid 24 from the pipeline portions leading from the bypassconduit 7 to the pet cocks 13, 14 and in order to fill and flush throughthose pipelines with a cleaning medium 28. The gas supply conduits arealso temporarily opened or supplied with clock pulses (cf. FIG. 4).

As a result of the leakage opening of the isolating valve 22 or of anincompletely closed isolating valve according to FIG. 6, respectively,both the liquid conduit 3 and the bypass conduit 7 are passed through bythe cleaning medium. The throttle 23 provides for an absorption ofpressure surges in liquid flows or in water flowing thereafter.

Instead of simultaneously flowing through the liquid conduit 3 and thebypass conduit 7, it is also possible to alternatively open and closethe isolating valves 15 and 22 during the cleaning cycle in a pulsatingfashion so that the cleaning medium will flow, in a pulsating way,through the conduits 3 and 7 in batches.

In order to be able to carry out a product change, i.e., for instance,to completely remove the cleaning liquid, the first and the secondisolating valves 11, 12 are first of all closed, the pet cocks 13, 14are opened and the section between the first and the second isolatingvalves 11, 12 of the bypass conduit 7 is flooded with gas. Thereby, thethird isolating valve 15 is suitably closed. The fourth isolating valve22 is opened so that the liquid now freshly flowing in through theliquid conduit after the cleaning liquid will displace the same. Uponremoval of the cleaning liquid, the first and the second isolatingvalves 11, 12 are opened and the pet cocks 13, 14 are closed so that thenormal condition as illustrated in FIG. 3 will be restored whileconveying the liquid via the liquid conduit 3. An analogue procedure isfollowed if the conveyance changes from one product liquid to anotherproduct liquid.

From the charts of FIGS. 7 to 10, it can be seen to what extent pressuresurges can be attenuated by means of the device according to theinvention. FIG. 7, for instance, shows an attenuated pressure surgeduring a normal stop of the liquid transport, i.e. involving anelectronic attenuation, and FIG. 8 shows the pressure pattern alsoduring a normal stop, however, without the device 6 according to theinvention. It is not only possible to detect a markedly higher maximumpressure but also a high frequency of the slowly decaying pressureoscillations resulting in an enormous strain on the entire plant.

FIGS. 9 and 10 show similar charts regarding an instantaneous oremergency stop, respectively, of the liquid to be conveyed, namely FIG.9 with a device 6 according to the invention and FIG. 10 without adevice 6 according to the invention.

The invention is not limited to the exemplary embodiments as illustratedin the drawing but can be modified in various respects. For instance,any pipeline departing from a point of the liquid conduit 3 and runninginto the liquid conduit 3 at another point or optionally also a pipelinesystem fulfilling the same function is conceived as a bypass conduit.Likewise, also the liquid conduit 3 can be constructed as a pipelinesystem.

1. A device for attenuating pressure surges of liquids flowing inside aliquid conduit and for cleaning the liquid conduit comprising: a bypassconduit that bridges over a section of the liquid conduit, wherein afirst isolating valve is disposed in the section of the liquid conduitbetween outlets of the bypass conduit and at least one lockable gassupply conduit is provided in the bypass conduit, and wherein the bypassconduit is divided into two gas-filled spaces by a second isolatingvalve disposed within the bypass conduit, a separate lockable gas supplyconduit running into each of the two spaces, both spaces communicatingwith the liquid conduit to attenuate pressure surges therein.
 2. Adevice according to claim 1, further comprising a third and fourthisolating valves disposed in the bypass conduit adjacent each outlet ofthe bypass conduit configured to separate the bypass conduit from theliquid conduit.
 3. A device according to claim 2, wherein a pet cock isprovided adjacent to each of the third and fourth isolating valves.
 4. Adevice according to claim 1, wherein the first isolating valve providedin the liquid conduit has, in the closed state, a leakage openingenabling a reduced flow.
 5. A device according to claim 1, wherein aprobe for determining a liquid level is disposed in each space of thebypass conduit.
 6. A device according to claim 5, further comprising acontrol unit coupled to the lockable gas supply conduits configured toinitiate an automatic gas flushing when the liquid level reaches apredetermined value to cause a discharge of liquid from the bypassconduit.
 7. A device according to claim 1, wherein each of the twogas-filled spaces is capable of being maintained at a different gaspressure using the separate lockable gas supply conduits.